Various methods for rolling aluminum and for providing the resultant rolled sheet with a given surface texture are known. A surface texture may be imparted to a sheet surface by a roll which has a surface textured by processes such as Electrical Discharge Texturing (EDT), roll grinding, cross hatch-grinding, ball or shot peening, etc. As used in the art, a “texture roll” would typically be defined as: a roll with a random or repeated pattern, isotropic or directional pattern of surface peaks and valleys with defined average heights and spacing for either aesthetic or functional purposes. The texture of the textured roll may be imparted to aluminum, steel and other metal surfaces, normally in a range of low reduction (3 to 10%) in a post cold rolling operation. For automotive sheet with an EDT texture, this is typically carried out as the last pass on a skin pass (temper) mill. The application of texture after cold rolling in a skin pass or a cold mill often results in limited transfer of the roll surface texture to the sheet due to the cold worked properties of the product, the size of the rolls and the low reductions employed. This may lead to the incoming surface not being totally eliminated or masked by the texture on the roll surface. This is particularly undesirable when features such as scratches or metal slivers from upstream processes are present. A sliver is defined as “A thin, elongated fragment of metal that has been rolled onto the surface of the parent metal and is attached by only one end.” (McGraw-Hill Dictionary Of Scientific And Technical Terms, Third Edition, p. 1491). Alternatively a sliver may be defined as a “Thin fragment of aluminum which is part of the material but only partially attached.” (Visual Quality Attributes of Aluminum Sheet and Plate, Al Assoc., 1994). Higher reductions with EDT rolls in cold rolling may also lead to more debris generation and diminishing the cleanliness of the sheet produced as a final product or as an intermediate product that is subjected to further processing.
In addition, a post cold rolling skin pass adds another step in the process which adds cost to the product. Improved and/or alternative methods and apparatus for imparting a desired surface texture to an aluminum sheet therefore remain desirable.